/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_negate_q15.c
*
* Description:	Negates Q15 vectors.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */
#include "arm_math.h"

/**
 * @ingroup groupMath
 */

/**
 * @addtogroup negate
 * @{
 */

/**
 * @brief  Negates the elements of a Q15 vector.
 * @param[in]  *pSrc points to the input vector
 * @param[out]  *pDst points to the output vector
 * @param[in]  blockSize number of samples in the vector
 * @return none.
 *
 * \par Conditions for optimum performance
 *  Input and output buffers should be aligned by 32-bit
 *
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function uses saturating arithmetic.
 * The Q15 value -1 (0x8000) will be saturated to the maximum allowable positive value 0x7FFF.
 */

void arm_negate_q15(
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{
	uint32_t blkCnt;                               /* loop counter */
	q15_t in;

#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q31_t in1, in2;                                /* Temporary variables */


	/*loop Unrolling */
	blkCnt = blockSize >> 2u;

	/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
	 ** a second loop below computes the remaining 1 to 3 samples. */
	while(blkCnt > 0u) {
		/* C = -A */
		/* Read two inputs at a time */
		in1 = _SIMD32_OFFSET(pSrc);
		in2 = _SIMD32_OFFSET(pSrc + 2);

		/* negate two samples at a time */
		in1 = __QSUB16(0, in1);

		/* negate two samples at a time */
		in2 = __QSUB16(0, in2);

		/* store the result to destination 2 samples at a time */
		_SIMD32_OFFSET(pDst) = in1;
		/* store the result to destination 2 samples at a time */
		_SIMD32_OFFSET(pDst + 2) = in2;


		/* update pointers to process next samples */
		pSrc += 4u;
		pDst += 4u;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x4u;

#else

	/* Run the below code for Cortex-M0 */

	/* Initialize blkCnt with number of samples */
	blkCnt = blockSize;

#endif /* #ifndef ARM_MATH_CM0 */

	while(blkCnt > 0u) {
		/* C = -A */
		/* Negate and then store the result in the destination buffer. */
		in = *pSrc++;
		*pDst++ = (in == (q15_t) 0x8000) ? 0x7fff : -in;

		/* Decrement the loop counter */
		blkCnt--;
	}
}

/**
 * @} end of negate group
 */
